The present invention generally relates to subterranean well completion apparatus and, in a preferred embodiment thereof, more particularly relates to coupling apparatus used to operatively interconnect various tubular well completion structures such as coil tubing sections, gas lift mandrels, packers, landing nipples and tubular sand screen sections.
In the fabrication of an well completion assembly using coil tubing, a required run of the coil tubing may be longer that the length of tubing carried on a supply reel. When this occurs, it is necessary to join two separate lengths of coil tubing together at facing end portions thereof. Because the two tubing lengths cannot conveniently be rotated relative to one another, the two conventional methods of connecting them are to weld them together or to connect them using swivel joints and lenz-type slip fittings. Because of fire hazards, the welding of coiled tubing at the rig site is considered highly undesirable, and quite often is not even permitted.
The swivel joint connection of two facing coil tubing ends requires that lenz-type slip fittings be secured to the facing tubing ends to provide them with connection thread areas. One end of the swivel joint is threadingly connected to one of the installed slip fittings and then rotated relative to the tubing lengths to threadingly connect the other end of the swivel joint to the other slip fitting. A similar coupling technique is used to connect various tubular well completion devices, such as landing nipples, packers, gas lift mandrels, circulating devices and tubular sand screen sections in an elongated overall length of coil tubing.
Over the length of a typical well completion assembly this conventional coupling technique tends to be a tedious, labor intensive, and therefore relatively expensive undertaking involving the use of numerous swivel joints and lenz-type slip fittings to connect the various tubular well completion devices between the corresponding sections of coil tubing, and to splice two lengths of coil tubing together where necessary. It can thus be seen that a need exists for improved apparatus for interconnecting facing end portions of coil tubing sections, and for operatively connecting tubular well completion devices in a length of coil tubing. It is accordingly an object of the present invention to provide such improved coupling apparatus.